Axillary Surgery in Breast Cancer: False Negative Results?

Sentinel node biopsy in the axilla as part of breast cancer surgery is standard of care. It has spared women from the requirement of a full axillary dissection, where many nodes are removed with resultant risks of long-term complications, such as arm swelling, or lymphedema. If a sentinel node biopsy is negative, that patient does not require further axillary surgery. So, how does a surgeon know a woman does not require further surgery at the time she is actual undergoing surgery? When patients are in the operating room and the surgeon is removing the sentinel nodes surgically, he asks the pathologist for a report on what those nodes contain, also known as an intraoperative report. If the report is negative, then there is no further surgery done in the axilla. But, what happens when the final report (usually days later) shows there was indeed cancer that had been missed in the intraoperative assessment? This "false-negative" result and it's implications on further treatment decisions and risk of relapse was the recent topic of a paper published in the American Journal of Surgery.

Tarras and colleagues looked at this issue as confronted at Swedish Cancer Institute in Seattle. Looking at patient, clinical data, surgical results, treatments rendered, and cancer outcomes, they found that the recurrence rate in women with a false negative sentinel node result Intraoperatively was 2%, far lower than the rate seen in women whose sentinel node result intraoperatively was positive (9%). This higher recurrence rate tracked with risks known to impact on recurrence already, such as large tumor size and absence of hormone receptors.

The importance of these findings is that the sentinel node biopsy result should be seen as an indicator of tumor volume. A falsely negative result did not appear to adversely effect recurrence, despite the fact that disease was ultimately discovered in the node. This tells us that treatment can be based on an overall assessment of tumor burden, and begs the question of whether or not further axillary surgery is needed in women who undergo a sentinel node biopsy, which is reported to be falsely negative.

Still, while provocative, most guidelines call for a full axillary node dissection if the sentinel node is ultimately found to contain cancer at the final analysis. Given this study was retrospective, it is unclear if the recurrence rate associated with the false negative result was due to other surgical procedures performed later, or the use of other modalities, such as chemotherapy. Ideally this question would be answered in a prospective randomized trial, but the ethics of such a trial would need to be fully elucidated.

For more information:

Taras AR, Hendrickson NA, Lowe KA, Atwood M, Beatty JD. Recurrence rates in breast cancer patients with false-negative intraoperative evaluation of sentinel lymph nodes. Am J Surg. 2010; 199:625-8.